Characterizations, genomic analysis, and antibioflim efficacy study of novel broadspectrum virulent bacteriophages Sfin-3, Sfin-4, and Sfin-5 targeting MDR clinical isolates of Shigella spp

The increasing prevalence of multidrug-resistant (MDR) Shigella species poses a serious global threat to public health and economy. Biofilm formation further complicates treatment due to enhanced resistance to antibiotics and host immune defenses, leading to persistent infections and increased morbidity. In this study, three novel lytic bacteriophages Sfin-3 , Sfin-4 and Sfin-5 were isolated from the river Ganga and evaluated for their therapeutic potential against Shigella flexneri (S. flexneri) , Shigella dysenteriae (S. dysenteriae) , and Shigella sonnei (S. sonnei) . These phages exhibited rapid adsorptions in 5–10 minutes, latent periods of 5–20 minutes, and burst sizes ranging from approximately 95 to 340 plaque-forming units (PFU) per infected cell. They remained stable across a wide pH spectrum and toleated thermal exposure of 60°C for one hour. Morphological analysis identified Sfin-3 , Sfin-4 , and Sfin-5 as members of the family Siphoviridae , characterized by isometric heads and long, non-contractile tails. Whole genome sequencing revealed that Sfin-3 , Sfin-4 and Sfin-5 harbor genomes of around 50 kb, with GC contents of around 45%. Comparative genomic and phylogenetic evaluations suggested that phages are genetically distinct from other reported phages and represent novel T1-like phage isolates. Importantly, Sfin-3 , Sfin-4 , and Sfin-5 displayed strong antibiofilm activity against developing and mature Shigella biofilm. Moreover, synergistic interactions with sub-MIC levels of azithromycin or ceftriaxone significantly enhanced biofilm eradication. Compared to earlier Sfin phages, these isolates exhibit broader host range and superior antibiofilm efficacy, highlighting their potential as alternative or adjunct therapeutic agents against MDR Shigella infections.